Apparatus for injecting gas into a vessel

ABSTRACT

An apparatus for injecting gas into a vessel is disclosed. The apparatus comprises a gas flow duct from which to discharge gas from the duct, an elongate central structure extending within the gas flow duct from its rear end to its forward end, and a plurality of flow directing vanes disposed about the central structure adjacent the forward end of the duct. The forward end of the central structure and the vanes are water cooled by separate supply passages.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Phase application based onPCT/AU2009/001606 filed on Dec. 11, 2009, the contents of which areincorporated herein by reference and claims the priority of AustralianApplication No. 2008906395, filed on Dec. 11, 2008, the contents ofwhich are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to an apparatus for injecting gas into avessel. It has particular, but not exclusive application to apparatusfor injecting a flow of gas into a metallurgical vessel under hightemperature conditions. Such metallurgical vessel may for example be asmelting vessel in which molten metal is produced by a direct smeltingprocess.

A known direct smelting process, which relies on a molten metal layer asa reaction medium, and is generally referred to as the Hlsmelt process,is described in U.S. Pat. Nos. 6,440,356 and 6,673,305.

The HIsmelt process comprises:

-   -   (a) forming a bath of molten metal in the form of iron and slag        in a vessel;    -   (b) injecting into the bath:        -   (i) a metalliferous feed material, typically metal oxides;            and        -   (ii) a solid carbonaceous material, typically coal, which            acts as a reductant of the metal oxides and a source of            energy; and    -   (c) smelting metalliferous feed material to metal in the metal        layer.

The term “smelting” is herein understood to mean thermal processingwherein chemical reactions that reduce metal oxides take place toproduce liquid metal.

The HIsmelt process also comprises post-combusting reaction gases, suchas CO and H₂ released from the bath in the space above the bath withoxygen-containing gas and transferring the heat generated by thepost-combustion to the bath to contribute to the thermal energy requiredto smelt the metalliferous feed materials.

The HIsmelt process also comprises forming a transition zone above thenominal quiescent surface of the bath in which there is a favourablemass of ascending and thereafter descending droplets or splashes orstreams of molten metal and/or slag which provide an effective medium totransfer to the bath the thermal energy generated by post-combustingreaction gases above the bath.

In the HIsmelt process the metalliferous feed material and solidcarbonaceous material is injected into the metal layer through a numberof lances/tuyeres which are inclined to the vertical so as to extenddownwardly and inwardly through the side wall of the smelting vessel andinto the lower region of the vessel so as to deliver the solids materialinto the metal layer in the bottom of the vessel. To promote the postcombustion of reaction gases in the upper part of the vessel, a blast ofhot air, which may be oxygen enriched, is injected into the upper regionof the vessel through the downwardly extending hot air injection lance.To promote effective post combustion of the gases in the upper part ofthe vessel, it is desirable that the incoming hot air blast exit thelance with a swirling motion. To achieve this, the outlet end of thelance may be fitted with internal flow guides to impart an appropriateswirling motion. The upper regions of the vessel may reach temperaturesof the order of 2000° C. and the hot air may be delivered into the lanceat temperatures of the order of 1100-1400° C. The lance must thereforebe capable of withstanding extremely high temperatures both internallyand on the external walls, particularly at the delivery end of the lancewhich projects into the combustion zone of the vessel.

-   -   The present invention provides a lance construction which        enables the relevant components to be internally water cooled        and to operate in a very high temperature environment.

SUMMARY OF THE INVENTION

According to the invention, there is provided an apparatus for injectinggas into a vessel, comprising:

-   -   a gas flow duct extending from a rear end to a forward end from        which to discharge gas from the duct;    -   an elongate central structure extending within the gas flow duct        from its rear end to its forward end;    -   a plurality of flow directing vanes disposed about the central        structure adjacent the forward end of the duct to impart swirl        to a gas flow through the forward end of the duct, the forward        end of the central structure and the forward end of the duct        co-acting together to form an annular nozzle for flow of gas        from the duct with swirl imparted by the vanes;    -   first cooling water flow passage means located within the        forward end of the central structure for flow of cooling water        to internally water cool outer surfaces of the forward end of        the central structure;    -   second cooling water flow passage means located within the vanes        for flow of cooling water to internally water cool the vanes;    -   a first cooling water supply passage within the central        structure for supplying a first flow of cooling water forwardly        through the central structure from its rear end and into the        first cooling water flow passage means in the forward end of the        central structure;    -   a second cooling water supply passage within the central        structure for supplying a second separate flow of cooling water        forwardly through the central structure from its rear end and        into the second cooling water flow passage means within the        vanes; and    -   water flow return passage means within the central structure for        return flow of water from the first and second cooling water        flow passage means.

The water return passage means may comprise a single flow passage forreturn flow of water from both the first and second cooling waterpassage means.

The first cooling water supply passage may extend as a central passagethrough the central structure for flow of water directly to the forwardend of the central structure.

The first cooling water supply passage may extend through the centralstructure for flow of water directly to a tip of the forward end of thecentral structure.

The second cooling water supply passage may comprise an annular passageformed within the central structure about the first supply passage.

The water return passage means may comprise a further annular passageformed within the central structure outside the annular second coolingwater supply passage.

The forward end of the central structure may include a domed noseportion and the first cooling water flow passage means may comprise acooling water flow passage extending from the tip of the nose for flowof cooling water around and backwardly along the nose.

The cooling water flow passage of the first cooling water flow passagemeans may extend in a spiral formation backwardly from the nose. Morespecifically that passage may extend in a single spiral extending fromthe tip of the nose to direct water in a single flow around andbackwardly along the nose to cool the nose with a single coherent streamof cooling water.

The cooling water flow passage of the first cooling water flow passagemeans may extend backwardly from the nose and within the outer peripheryof that part of the central structure about which the vanes aredisposed.

The cooling water flow passage of the first cooling water flow passagemeans may bypass the water flow path from the second water supplypassage to the second cooling water flow passage means within the vanes.

A forward portion of the second cooling water supply passage may beformed as an arcuate passage having first and second end portionsseparated by an arcuate region of extent greater than 180 degrees andless than 360 degrees and a segmental region between the first andsecond end portions, and wherein the cooling water flow passage of thefirst cooling water flow passage means may extend within the segmentalregion and thereby bypass the forward portion of the second coolingwater supply passage.

The cooling water flow passage of the first cooling water flow passagemeans may include an inward lateral step that bypasses the water flowpath from the second water supply passage to the second cooling waterflow passage means within the vanes.

The cooling water flow passage of the first cooling water flow passagemeans may extend backwardly from the diversion and be connected to thewater return passage means.

The second cooling water flow passage means may comprise passages in thevanes extending between inlets at forward ends of the vanes and outletsat rearward ends of the vanes.

The second cooling water supply passage may connect with the vanepassage inlets at the forward ends of the vanes.

The vane passage outlets at the rear ends of the vanes may connect withthe cooling water return passage means.

Each vane may have a hollow interior divided by baffles defining thevane passage within the vane.

The baffles may be arranged such that the vane passage extends back andforth along the vane so that cooling water flowing from the inlet to theoutlet flows in a plurality of passes from the front to the rear end ofthe vane.

The first pass of each vane passage may extend from the inlet along theouter longitudinal edge of the vane.

The invention also extends to apparatus for location within a gas flowduct through which to inject gas into a vessel, said apparatuscomprising:

-   -   an elongate structure to extend within the gas flow duct;    -   a plurality of flow directing vanes disposed about the elongate        structure adjacent a forward end of the structure to impart        swirl to a gas flow through the duct;    -   first cooling water flow passage means located within the        forward end of the elongate structure for flow of cooling water        to internally water cool outer surfaces of the forward end of        the elongate structure;    -   second cooling water flow passage means located within the vanes        for flow of cooling water to internally water cool the vanes;    -   a first cooling water supply passage within the elongate        structure for supplying a first flow of cooling water forwardly        through the elongate structure from its rear end and into the        first cooling water flow passage means in the forward end of the        central structure;    -   a second cooling water supply passage within the elongate        structure for supplying a second separate flow of cooling water        forwardly through the elongate structure from its rear end and        into the second cooling water flow passage means within the        vanes; and    -   water flow return passage means within the elongate structure        for return flow of water from the and second cooling water flow        passage means.

In order that the invention may be more fully explained, one particularembodiment will be described in detail with reference to theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical section through one embodiment of a direct smeltingvessel incorporating a pair of solids injection lances and a hot airblast injection lance constructed in accordance with the invention;

FIG. 2 is a longitudinal cross-section through the hot air blastinjection lance;

FIG. 3 is a longitudinal cross-section through a central structure ofthe lance;

FIG. 4 is a longitudinal cross-section through a forward part of thecentral structure;

FIG. 5 is a transverse cross-section on the line 5-5 in FIG. 4;

FIGS. 6 and 7 are side elevations that show the forward part of thecentral structure with some parts removed for clarity;

FIG. 8 is a perspective view of a swirl vane structure mounted on theforward end of the central structure;

FIG. 9 is a side elevation of the swirl vane structure;

FIG. 10 is a development of one of the swirl vanes in the structureshown in FIGS. 8 and 9; and

FIG. 11 is a transverse cross-section through one of the swirl vanes.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 illustrates a direct smelting vessel suitable for operation bythe HIsmelt process as described in U.S. Pat. Nos. 6,440,356 and6,673,305. The metallurgical vessel is denoted generally as 11 and has ahearth that includes a base 12 and sides 13 formed from refractorybricks; side walls 14 which form a generally cylindrical barrelextending upwardly from the sides 13 of the hearth and which includes anupper barrel section 15 and a lower barrel section 16; a roof 17; anoutlet 18 for off-gases; a forehearth 19 for discharging molten metalcontinuously; and a tap-hole 21 for discharging molten slag.

In use, the vessel contains a molten bath of iron and slag whichincludes a layer 22 of molten metal and a layer 23 of molten slag on themetal layer 22. The arrow marked by the numeral 24 indicates theposition of the nominal quiescent surface of the metal layer 22 and thearrow marked by the numeral 25 indicates the position of the nominalquiescent surface of the slag layer 23. The term “quiescent surface” isunderstood to mean the surface when there is no injection of gas andsolids into the vessel.

The vessel is fitted with a downwardly extending hot air injection lance26 for delivering a hot air blast into an upper region of the vessel andtwo solids injection lances 27 extending downwardly and inwardly throughthe side walls 14 and into the slag layer 23 for injecting iron ore,solid carbonaceous material, and fluxes entrained in an oxygen-deficientcarrier gas into the metal layer 22. The position of the lances 27 isselected so that their outlet ends 28 are above the surface of the metallayer 22 during operation of the process. This position of the lancesreduces the risk of damage through contact with molten metal and alsomakes it possible to cool the lances by forced internal water coolingwithout significant risk of water coming into contact with the moltenmetal in the vessel.

The construction of the hot air injection lance 26 is illustrated inFIGS. 2-11. As shown in these figures lance 26 comprises an elongateduct 31 which receives hot gas through a gas inlet structure 32 andinjects it into the upper region of vessel. The lance includes anelongate central tubular structure 33 which extends within the gas flowduct 31 from its rear end to its forward end. Adjacent the forward endof the duct, central structure 33 carries a series of four swirlimparting vanes 34 for imparting swirl to the gas flow exiting the duct.The forward end of central structure 33 has a domed nose 35 whichprojects forwardly beyond the tip 36 of duct 31 so that the forward endof the central structural 33 and the forward end of the duct co-acttogether to form an annular nozzle for divergent flow of gas from theduct with swirl imparted by the vanes 34. Vanes 34 form part of astructure 40 comprising a tubular hub 40A about which the vanes 34 aredisposed in a four-start helical formation and are a sliding fit withinthe forward end of the duct.

The wall of the main part of duct 31 extending downstream from the gasinlet 32 is internally water cooled. This section of the duct iscomprised of a series of three concentric steel tubes 37, 38, 39extending to the forward end part of the duct where they are connectedto the duct tip 36. The duct tip 36 is of hollow annular formation andit is internally water cooled by cooling water supplied and returnedthrough passages in the wall of duct 31. Specifically, cooling water issupplied through an inlet 41 and annular inlet manifold 42 into an innerannular water flow passage 43 defined between the tubes 38, 39 of theduct through to the hollow interior of the duct tip 36 throughcircumferentially spaced openings in the tip. Water is returned from thetip through circumferentially spaced openings into an outer annularwater return flow passage 44 defined between the tubes 37, 38 andbackwardly to a water outlet 45 at the rear end of the water cooledsection of duct 31.

The water cooled section of duct 31 is internally lined with an internalrefractory lining 46 that fits within the innermost metal tube 39 of theduct and extends through to the water cooled tip 36 of the duct. Theinner periphery of duct tip 36 is generally flush with the inner surfaceof the refractory lining which defines the effective flow passage forgas through the duct. The forward end of the refractory lining has aslightly reduced diameter section 47 which receives the swirl vanes 34with a snug sliding fit. Rearwardly from section 47 the refractorylining is of slightly greater diameter to enable the central structure33 to be inserted downwardly through the duct on assembly of the lanceuntil the swirl vanes 34 reach the forward end of the duct where theyare guided into snug engagement with refractory section 47 by a taperedrefractory land 48 which locates and guides the vanes into therefractory section 47.

The hollow interior of duct tip 36 may be divided internally so as toform cooling water flow galleries (not shown) extendingcircumferentially around the tip in the manner which is more fullydisclosed in United States Patent Publication 2006-0108722-A1.

As is to be described in detail with reference to FIGS. 8 to 11 theswirl vanes 34 are formed with internal cooling water flow passages. Thevanes 34 and the front end of central structure 33 are internally watercooled by cooling water supplied forwardly through the central structurefrom the rear end to the forward end of the lance and then returned backalong the central structure to the rear end of the lance. Separate watersupply passages extend through the central structure for supply ofcooling water to the vanes and to the domed nose 35 so as to enable astrong flow of cooling water directly to the vanes and to the domed nose35 in particular which are subjected to very high heat flux in operationof the lance.

Central structure 33 comprises a series of three concentric steel tubes49, 50, 51 each of which is formed by tube segments disposed end to endand welded together. Inner tube 49 defines a central first water flowpassage 52 through which water flows forwardly through the centralstructure from a water inlet 53 at the rear end of the lance through tothe front end nose 35 of the central structure. A second water supplypassage 54 is formed by the annular space between the inner tube 49 andthe intermediate tube 50 through which water can flow through thecentral structure from a water inlet 60 at the rear end of the lance tointernal cooling water flow passages in the swirl vanes 34.

The annular space between the intermediate tube 50 and the outer tube 51provides a water return passage 56 through which cooling water returnsfrom both the nose 35 of the central structure 33 and the cooling waterflow passages in the vanes back through the central structure to a wateroutlet 55 at the rear end of the lance.

Toward the front end of the central structure 33 the intermediate tube50 and outer tube 51 flare outwardly at 51A, 52A so that the inner endof the second water supply passage 54 is enlarged. Intermediate tube 51Ais extended by an extension tube 80 which is connected to a tubular rearpart of a copper body 61 fitted within an outer domed nose shell 62 alsoformed of copper forming the nose end of central structure 33.

The tubular hub 40A of vane structures fits around the rear end of body61 and the extension tube 80 immediately behind the nose shell 62. Theforward end of vane hub 40A fits onto a circumferential rib 82 formed onthe tubular part of copper body 61 and provided with an annular groove83 which receives water through four circumferentially spaced slots 84through the tubular part of copper body 61 to serve as a water inletgallery for supply of cooling water from the expanded inner end ofcooling water passage 54 to the cooling water passages in the vanes inthe manner to be described below.

Behind rib 82 there is an annular clearance space 90 between the hub 40Aof the vane structure and the extension tube 80 and tubular part ofcopper body 61 which provides an extension of a water flow passagethrough the front end of the central structure in the manner now to bedescribed.

The inner copper piece 61 of the nose end of the central structure isformed with a central water flow passage 63 connecting through aconnector tube 70 with the inner end of central water supply passage 52to receive water from the duct 52 and direct it to the tip of the nose.Nose piece 61 is formed with projecting ribs 64 which fit snugly withinthe nose shell 62 to define a single continuous cooling water flowpassage 65 between the inner section 61 and the outer nose shell 62. Theribs 64 are shaped so that the single continuous passage 65 extends asannular passage segments 66 interconnected by passage segments 67sloping from one annular segment to the next. Thus passage 65 extendsfrom the tip of the nose in a spiral which, although not of regularhelical formation, does spiral around and back along the nose.

The rear end of copper piece 61 is formed with an integral cylindricalboss 104 within which there extends a short longitudinal passage 85connected at its forward end with the rear end of the nose cooling waterpassage 65 through a port 86 and at its rear end through a port 87 withthe annular space 90 within the vane structure hub 40A. In effect, thisarrangement forms an inward lateral step in the flow passage. Coolingwater from passage 65 can thus flow via port 86, passage 85 and port 87into the annular space 90, so bypassing the outward flow of coolingwater to the vanes via the circumferentially spaced slots 84 and thegroove 83 in rib 82. More particularly, the cylindrical boss 104 extendsthrough what would have been an annular forward end portion of thesecond cooling water supply passage 54, with the result that the forwardend is an arcuate section 106 as viewed in FIG. 5. This arcuate section106 has first and second end portions 108, 110 separated by thecylindrical boss 104. It can be appreciated from FIG. 5 that thearrangement does not restrict water flow from the forward end of thesecond cooling water supply passage 54 into the slots 84 thatcommunicate with the annular groove 83 and the cooling water passages inthe vanes in the manner to be described below. Annular space 90 isdivided by an elongate baffle bar 88 to form a spiraled extension of thecooling water passage 65 extending around the front end of the innerstructure immediately within the vaned structure 40 and back to anannular water outlet gallery 89 which connects with the water returnpassage 56 of the central structure. The water passage 65 and thespiraled extension within the annular space 90 thus form a continuouscooling water flow passage in the forward end of the central structurewhich extends backwardly from the nose and within the outer periphery ofthat part of the central structure on which the vanes are mounted soassisting in the cooling of the vane structure, the diversion throughpassage 85 enabling this passage to bypass the outward flow of coolingwater to the vanes.

The forced flow of cooling water in a single coherent stream throughspiral passage 65 extending around and back along the nose end 35 ofcentral structure ensures efficient heat extraction and avoids thedevelopment of “hot spots” on the nose which could occur if the coolingwater is allowed to divide into separate streams at the nose. In theillustrated arrangement the cooling water is constrained in a singlestream from the time that it enters the nose end 35 to the time that itexits the nose end.

The construction of vane structure 40 is illustrated in FIGS. 8 to 11.Each vane is formed by a pair of stainless steel side plates 91 whichspiral along hub 40A in the front to rear direction and are separated bya capping bar 92 extended around the outer rim of the vane and a pair ofbaffle bars 93, 94 which divide the interior of the vane between theside plates into an elongate internal cooling water flow passage 95. Thecooling water passages 95 in vanes 34 extend from inlets 96 formed atthe forward ends of the vanes by slots extended through the hub 40A toregister with the vane cooling water inlet gallery 83 and outlets 97formed by slots in the hub 40A at the rear ends of the vanes to registerwith the water outlet gallery 89 through which water can flow from thevanes back through the water return passage 56 to the rear end of thecentral structure 33. Baffles 93, 94 are formed such that the water flowpassages 95 extend from the inlets 96 backwardly along outer parts ofthe vanes to the rear end of the vanes then forwardly back to theforward end of the vanes before passing back along the inner parts ofthe vanes to the outlets 97. Thus incoming cooling water is directedfirstly to the outer edges of the vanes which are most susceptible toexcessive heating and degradation. The multi-pass flow passages 95 alsoensure that all parts of the vanes are effectively cooled and stagnantwater flow passages cannot develop.

The internally water cooled stainless steel swirl vanes are very robustand are able to withstand extremely high temperature conditions andabrasion from grit or other material carried by the hot gas blast withinthe lance. The vanes may be hard faced for maximum life.

Inner structure is provided with an external heat shield 91 formed ofrefractory material 92 encased within an outer casing 93 of hightemperature resistant stainless steel to shield against heat transferfrom the incoming hot gas flow in the duct 31 into the cooling waterflowing within the central structure 33. The heat shield reduces heattransfer into the water flowing to the inner end of the centralstructure and the vanes and also insulates the returning water from thehot gas within the lance and hence minimise the load on cooling circuitsfor the cooling water.

The invention claimed is:
 1. Apparatus for injecting gas into a vessel,comprising: a gas flow duct extending from a rear end to a forward endfrom which to discharge gas from the duct; an elongate central structureextending within the gas flow duct from its rear end to its forward end;a plurality of flow directing vanes disposed about the central structureadjacent the forward end of the duct to impart swirl to a gas flowthrough the forward end of the duct, the forward end of the centralstructure and the forward end of the duct co-acting together to form anannular nozzle for flow of gas from the duct with swirl imparted by thevanes; first cooling water flow passage means located within the forwardend of the central structure for flow of cooling water to internallywater cool outer surfaces of the forward end of the central structure;second cooling water flow passage means located within the vanes forflow of cooling water to internally water cool the vanes; a firstcooling water supply passage within the central structure for supplyinga first flow of cooling water forwardly through the central structurefrom its rear end and into the first cooling water flow passage means inthe forward end of the central structure; a second cooling water supplypassage within the central structure for supplying a second separateflow of cooling water forwardly through the central structure from itsrear end and into the second cooling water flow passage means within thevanes; and water flow return passage means within the central structurefor return flow of water from the first and second cooling water flowpassage means.
 2. Apparatus as claimed in claim 1, wherein the waterreturn passage means comprises a single flow passage for return flow ofwater from both the first and second cooling water passage means. 3.Apparatus as claimed in claim 1, wherein the first cooling water supplypassage extends as a central passage through the central structure forflow of water directly to the forward end of the central structure. 4.Apparatus as claimed in claim 3, wherein the first cooling water supplypassage extends through the central structure for flow of water directlyto a tip of the forward end of the central structure.
 5. Apparatus asclaimed in claim 3, wherein the second cooling water supply passagecomprises an annular passage formed within the central structure aboutthe first cooling water supply passage.
 6. Apparatus as claimed in claim5, wherein the water return passage means comprises a further annularpassage formed within the central structure outside the annular secondcooling water supply passage.
 7. Apparatus as claimed in claim 1,wherein the forward end of the central structure includes a domed noseand the first cooling water flow passage means comprises a cooling waterflow passage extending from a tip of the nose for flow of cooling wateraround and backwardly along the nose.
 8. Apparatus as claimed in claim7, wherein the cooling water flow passage of the first cooling waterflow passage means extends in a spiral formation backwardly from thenose.
 9. Apparatus as claimed in claim 8, wherein the cooling water flowpassage of the first cooling water flow passage means extends in asingle spiral extending from the tip of the nose to direct water in asingle flow around and backwardly along the nose to cool the nose with asingle coherent stream of cooling water.
 10. Apparatus as claimed inclaim 9, wherein the cooling water flow passage of the first coolingwater flow passage means extends backwardly from the nose and within theouter periphery of that part of the central structure about which thevanes are disposed.
 11. Apparatus as claimed in claim 10, wherein thecooling water flow passage of the first cooling water flow passage meansincludes bypasses the water flow path from the second water supplypassage to the second cooling water flow passage means within the vanes.12. Apparatus as claimed in claim 11, wherein a forward portion of thesecond cooling water supply passage is formed as an arcuate passagehaving first and second end portions separated by an arcuate region ofextent greater than 180 degrees and less than 360 degrees and asegmental region between the first and second end portions, and whereinthe cooling water flow passage of the first cooling water flow passagemeans extends within the segmental region and thereby bypasses theforward portion of the second cooling water supply passage. 13.Apparatus defined in claim 12 wherein the cooling water flow passage ofthe first cooling water flow passage means includes an inward lateralstep that bypasses the water flow path from the second water supplypassage to the second cooling water flow passage means within the vanes.14. Apparatus as claimed in claim 13, wherein the cooling water flowpassage of the first cooling water flow passage means extends backwardlyfrom the lateral step and is connected to the water return passagemeans.
 15. Apparatus as claimed in claim 1 wherein the second coolingwater flow passage means comprises passages in the vanes extendingbetween inlets at forward ends of the vanes and outlets at rearward endsof the vanes.
 16. Apparatus as claimed in claim 15, wherein the secondcooling water supply passage connects with the vane passage inlets atthe forward ends of the vanes.
 17. Apparatus as claimed in claim 16,wherein the vane passage outlets at the rear ends of the vanes connectwith or are in close proximity to the cooling water return passagemeans.
 18. Apparatus as claimed in claim 17 wherein each vane has ahollow interior divided by baffles defining the cooling water passagewithin the vane.
 19. Apparatus as claimed in claim 18, wherein thebaffles are arranged such that the cooling water passage extends backand forth along the vane so that cooling water flowing from the inlet tothe outlet flows in a plurality of passes from the front to the rear endof the vane.
 20. Apparatus as claimed in claim 19, wherein the firstpass of each vane passage extends from the inlet along the outerlongitudinal edge of the vane.
 21. Apparatus for location within a gasflow duct through which to inject gas into a vessel, said apparatuscomprising: an elongate structure to extend within the gas flow duct; aplurality of flow directing vanes disposed about the elongate structureadjacent a forward end of the structure to impart swirl to a gas flowthrough the duct; first cooling water flow passage means located withinthe forward end of the elongate structure for flow of cooling water tointernally water cool outer surfaces of the forward end of the elongatestructure; second cooling water flow passage means located within thevanes for flow of cooling water to internally water cool the vanes; afirst cooling water supply passage within the elongate structure forsupplying a first flow of cooling water forwardly through the elongatestructure from its rear end and into the first cooling water flowpassage means in the forward end of the central structure; a secondcooling water supply passage within the elongate structure for supplyinga second separate flow of cooling water forwardly through the elongatestructure from its rear end and into the second cooling water flowpassage means within the vanes; and water flow return passage meanswithin the elongate structure for return flow of water from the secondcooling water flow passage means.